Abstract
We have previously demonstrated that cultured CCD cells deprived of aldosterone develop a loss of Na+ reabsorptive activity and a loss of the cellular recycling compartment for ENaC. The recycling compartment and Na+ reabsorptive phenotype are restored over time by aldosterone. Restoration of the ENaC recycling pathway is associated with up‐regulation of multiple proteins in the endosomal compartment. Analysis of early endosomes isolated from CCD cells under these conditions using Two‐dimensional difference gel electrophoresis (DIGE) or Isobaric tag for relative and absolute quantitation (iTRAQ) indicates that aldosterone significantly up‐regulates 15‐20 distinct proteins. One major protein induced is Annexin 2 (Ann2). Ann2 has been implicated in both exocytic and endocytic pathways and has been described to form a functional complex with CFTR. Ann2 colocalizes with Rab11 endosomes and is more abundant in these endosomes with the addition of aldosterone. Knockdown of Ann2 in CCD cells results in a decrease of basal and forskolin induced ENaC activity. These results suggest that Ann2 localizes to recycling endosomes upon addition of aldosterone and facilitates the recycling of ENaC.
Published Version
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